Volume 8 Issue 9, September 2012

Type IV collagen, a major constituent of basement membranes, contains an unusual intermolecular sulfilimine crosslink whose route of biosynthesis has remained undefined. An oxidative triad consisting of peroxidasin, H₂O₂ and halide is now shown to drive sulfilimine generation in vivo.

Glycosyltransferases, enzymes that catalyze glycosidic bond formation, are one of the most important but least well-characterized protein families found in nature. A new label-free, high-throughput glycan array–based strategy enables rapid profiling of tens of thousands of potential glycosyltransferase reactions.

Single-molecule observations reveal that lipid- and protein-based interactions jointly contribute to the interactions among glycosylphosphatidylinositol-anchored proteins in membranes. Understanding these interactions will help to refine long-evolving (and still debated) models of 'raft' domains in biological membranes.

AWP28, an activity-based probe for caspase-1, reveals that caspase-1 is required to bypass apoptosis for pyroptotic cell death during bacterial infection of macrophages.

Genetic code expansion by ribosomal incorporation of non-natural amino acids has provided a useful approach for site-specific protein modification. This approach has now been extended to the model organism Drosophila melanogaster, permitting the introduction of non-standard amino acids into proteins within specific cell and tissue types and across developmental stages.

AID/APOBEC deaminases, which convert cytosine bases to uracils in DNA and RNA, have recently been assigned a role in epigenetic regulation as components of DNA demethylation pathways. A systematic study shows that AID/APOBEC enzymes preferentially deaminate unmodified cytosine over its C5-modified forms, calling into question the plausibility of deaminase-mediated DNA demethylation pathways.

Application of a new thermal light scattering technique to quantitatively analyze nearly 150 mutants of the rhomboid intramembrane protease GlpG, coupled with thermodynamic measurements and protease assays, reveals how interactions throughout the molecule collaborate to support enzyme structure and function.

Discovery of the native activity of the ~60,000 putative glycosyltransferases remains a substantial challenge. A high-throughput, label-free method drastically speeds this process, with assays of 85 enzymes, 24 acceptors and 7 donors returning functions for four new proteins.

Single-molecule imaging reveals that GPI-anchored proteins in the plasma membrane form homodimer rafts via ectodomain protein interactions. Raft-lipid interactions stabilize higher order oligomers, which trigger intracellular signaling upon ligand binding.

Peroxidasin uses hypohalous acid oxidants to catalyze the formation of sulfilimine bonds in basement membranes.

A study of three synthetases involved in streptothricin biosynthesis demonstrates roles for two A domains in activating lysine, with one A domain transferring lysine to a carrier T domain and the second directly catalyzing amide bond formation to form a growing lysine oligopeptide.

The plant hormone auxin affects many aspects of root development, including lateral root branching. A high-throughput screen in Arabidopsis thaliana has led to the identification of naxillin, a non-auxin chemical probe that enhances lateral root branching and has revealed an important role of the root cap in regulating this process.